Power generation plants produce electricity by converting an energy source (e.g. fossil fuel, nuclear fusion, hydraulic heat and geothermal heat) into mechanical energy (e.g. rotation of a turbine shaft), and subsequently converting the mechanical energy into electrical energy (e.g. by the principles of electromagnetic induction). Some power generation plants, such as a turbogenerator, comprise a turbine, a generator and an exciter. Typically, the turbine, the generator and the exciter are coupled to each other in axial alignment, with the generator located between the turbine and the exciter.
The output of the turbine is mechanical energy in the form of turbine shaft rotation which is then converted into electrical energy by the generator. The generator includes an axially extending rotor surrounded and sleeved by an annular stator of the generator. The rotor includes a shaft on which conductive coil windings are axially arranged and which is capable of rotating inside the stator. The turbine shaft rotates the generator rotor shaft, and the exciter through a shaft provides an electric current to the conductive coil windings of the shaft of the rotor. The rotating electrically charged rotor creates a magnetic flux that induces an electric current in stationary stator coil windings present in the stator. This induced electric current is then drawn from the stator and constitutes the electricity that the power generation plant provides.
One prerequisite of the above-described power generation scheme is the electrical interconnection of the exciter and the generator enabling the exciter to provide the electric current to the conductive coil windings in the rotor shaft. An electric current is transported in a closed loop configuration from an electrical interface of the shaft of the exciter to an electrical interface of the shaft of the generator. The electric current subsequently flows to the generator rotor coil windings, and then back to the exciter.
Typically, the electrical interfaces are located at axial leads of the shafts of the generator and the exciter and are either a ‘butterfly type’ or a ‘pin type’ electrical interface.
In the ‘butterfly type’ electrical interface there are at least two flattened strips, made of electrically conducting material, positioned on a surface at the axial lead of the generator or the exciter such that they can establish an electrical connection by physical contact with similarly structured and similarly oriented two counterpart conducting strips positioned on a surface at the axial lead of the exciter or the generator, respectively.
In ‘pin type’, there is a male part and a female part, each made of electrically conducting material. The male part includes at least two pins and the female part includes at least two receptacles, each receptacle suitable to receive one pin of the male part though an opening of the receptacle.
The electrical connection between the generator and the exciter is established by inserting the pins into the receptacles, and thereby physically and electrically connecting the pins and the receptacles.
In one variation of the pin type, the male part is positioned extending out from a surface at the axial lead of the generator and the female part is located at the exciter with the openings of the receptacles positioned on a surface at the axial lead of the exciter. In an alternate variation of the pin type, the male part is positioned extending out from the surface at the axial lead of the exciter and the female part is located at the generator with the openings of the receptacles positioned on the surface at the axial lead of the generator.
In yet another variation of the pin type electrical interface, the generator and the exciter both have female parts i.e. the receptacles are provided on the rotor shaft with openings of the receptacles on the surface at the axial lead of the generator. Similarly, the receptacles are also provided on the exciter shaft with openings of the receptacles on the surface at the axial lead of the exciter shaft. Subsequently, the male part having the pins is introduced as an additional component between the female part of the generator and the female part of the exciter, wherein for each pin, one portion of the pin is inserted into the openings of the receptacles of the rotor of the generator and another portion of the pin is inserted into the openings of the receptacles of the shaft of the exciter.
It may be noted that butterfly type connection does not conform to pin type connection and thus an electrical connection can only be established between a generator and an exciter if the electrical interfaces of the generator and the exciter are either both of the pin type or both of the butterfly type. A generator having the pin type interface is incompatible to be physically coupled to an exciter having the butterfly type interface for establishing an electrical connection. Similarly, a generator having the butterfly type interface is incompatible to be physically coupled to an exciter having the pin type interface for establishing an electrical connection. This limitation requiring only specific pairing of the electrical interface of the generator and the exciter is a disadvantage.